Pulse timing system



3 Sheets-Sheet 1 R. R. WILLIAMSON PULSE TIMING SYSTEM May 26, 1964 Filed Deo.

May 26, 1964 R. R. WILLIAMSON PULSE TIMING SYSTEM Filed Dec. 20, 1955 3 Sheets-Sheet 2 May 26, 1964 R. R. WILLIAMSON PULSE TIMING SYSTEM Filed Dec. 20, 1955 3 Sheets-Sheet 5 ATTORNEY United States Patent Oil dce 3,134,976 Patented May 26, 1964 3,134,976 PULSE TIMING SYSTEM Robert R. Williamson, Sunland, Calif., assignor to General Precision, Inc., a corporation of Delaware Filed Dec. 20, 1955, Ser. No. 554,158 20 Claims. (Cl. 343-13) This invention relates to a timing system and more particularly to a system for accurately determining the time between a transmitted pulse and the reflections of the pulse back to the transmitting position from a distant object. The embodiment of the invention is particularly adapted to be used for measuring the distance between the -transmitter and a distant object as in radar systems.

Various apparatus has been built in the past number of years for using pulses to measure the distance between a transmitting position and a distant object. In such apparatus, the pulses are transmitted from the transmitting position and are reflected as echoes from the distant object back to the transmitting position. By measuring the time between the transmission and the reception of pulses, indications as to the distance between the transmitting position and the removed object can be obtained.

The apparatus now in use starts to measure time from the instant that the pulse is transmitted toward the distant object. The time is measured on an analogue basis by obtaining a voltage proportional to the time. The analogue voltage is obtained by triggering a variable delay line into a state of activation at the time of pulse transmission and by de-activating the delay line at the time of pulse reception. This method of determining time has failed to meet the need for increased accuracies which are required for determining the distance between the transmitting position and the removed object. The indications are somewhat inaccurate since sensitive diiferences in the amplitude of an analogue voltage cannot be easily measured.

In order to produce high accuracies such as those including errors of less than one yard, it has been recognized that digital techniques should be used, In such digital techniques, a plurality of signals would have to be produced to represent on a composite basis the time between the transmission and reception of the pulses. Various attempts have been made to use digital techniques but such systems have not been successful. One problem has been presented by the requirement that signals having frequencies as high as 30 megacycles have to be used in such previously proposed systems. Furthermore, stages stages having Wide band characteristics have to be used in order to pass signals in the range of to 30 megacycles for the production of a plurality of signals representing the output quantity in digital form. By using stages with wide band characteristics, sensitivity in the response of the stages becomes dulled. This necessitates the use of additional amplifier stages and increases the cost, weight, complexity and power consumption of the apparatus. It also hinders the use of transistors in such apparatus since transistors have relatively narrow band characteristics.

This invention provides a system for determining the distance between a transmitting position and a distant object with accuracies superior to those which have been obtained. The invention produces such accuracies by using digital techniques on a practical basis to measure and inidcate the time between the transmission and reception of pulses. The invention produces first signals at a fundamental frequency and other signals which are harmonics of the fundamental frequency. The system then combines all of the signals to produce a composite signal having a sharp leading edge. This sharp leading edge is differentiated to produce a spiked signal for triggering a transmitter. When the transmitter is triggered, it sends an energy pulse toward a removed object for reflection from the removed object.

When the reflected pulse is received from the removed object, it is recirculated to produce a plurality of clock signals. At each clock signal, a test is made as to the phase of a different one of the signals having the fundamental and harmonic frequencies. The test is made by a particular digital converter such that ambiguities in the results of the test are eliminated. The results obtained from the test indicate in digtial form the time between the transmission of the pulse and the reflection of the pulse by the removed object back to the transmitting position.

The apparatus constituting this invention eliminates certain disadvantages which would be obtained by the use of other digital techniques. The apparatus requires only stages having narrow band characteristics to produce the triggering signals. This eliminates the need for the additional ampliiier stages required in the prior apparatus and reduces the size, Weight and power consumption of the apparatus. It also permits the use of transistors such that further considerable reductions in size, weight and power consumption can be obtained.

In the drawings:

FIGURE 1 is a circuit diagram, mainly in block form, somewhat schematically illustrating transmitting apparatus forming one part of this invention;

FIGURE 2 is a circuit diagram, mainly in block form, somewhat schematically illustrating receiving apparatus forming another part of the invention;

FIGURE 3 is a circuit diagram, partly in block form, somewhat schematically illustrating phase testing apparatus forming a third part of the invention and includes certain stages also shown in FIGURES l and 2;

FIGURE 4 illustrates curves representing composite timing signals produced by certain stages shown in the previous gures and further representing the use of these timing signals to produce a pulse for transmission, and

FIGURE 5 illustrates curves representing the operation of the apparatus shown in FIGURE 3 in producing a plurality of signals representing in digital form the time between the transmission of a pulse and the reflection of the pulse back to the transmitting position.

In the embodiment of the invention shown in the drawings, signals from an oscillator 10 (FIGURE 1) are adapted to be introduced to a harmonic generator such as a frequency doubler 12. The oscillator 10 and the frequency doubler 12 are included in transmitting apparatus shown in FIGURE 1. The oscillator 1t) may be a conventional oscillator such as a Hartley or Colpitts oscillator described on pages 480 to 484, inclusive, of Radio Engineers Handbook by Frederick E. Terman and published by the McGraw Hill Book Company (First Edition, 1943). The doubler 12 may be a conventional circuit constructed in a manner similar to that disclosed on pages 458 to 462, inclusive, of said Radio Engineers Handboo by Frederick E. Terman.

The signals from the oscillator l0 are also adapted to be introduced to a pair of phase shift networks 14 and 16. The phase shift networks 14 and 16 may be constructed in a number of different ways, for example as described on pages 949 and 950 of said Radio Engineers Handbook, by Frederick E. Terman. The phase shift network 14 may operate on the signals from the oscillator 10 to shift the signals through a particular angle related to the frequency of the signals and related to the time from the reception of a pulse by the receiver 50 in FIGURE 2 to the formation of a particular clock signal. This will be described in detail subsequently. The phase shift provided by the network 16 may be different by a particular angle such as approximately 45 degrees relative to the phase shift provided by the network 14.

`provided by the network 20.

Vcascade arrangement.

The signals from the frequency doubler 12 are introduced to a doubler 18 which may be constructed in a manner similar to that of the doubler 12. The signals from the frequency doubler 12 are also introduced to a pair of phase shift networks 20 and 22. The phase shift networks 20 and 22 may be constructed in a manner similar to the networks 14 and 16. The network 20 may operate to shift the signals from the doubler 12 through an angle related to the frequency of the signals and to the time from the reception of a pulse bythe receiver 50 in FIGURE 2 to the formation ofv a particular clock signal. The phase shift provided by the network 22 may bedifferent by a suitable angle such as approximately 45 degrees with respect to the phase shift In like manner, the signals from the frequencydoubler 18 are introduced to a frequency doubler (not shown) corresponding in construction andV operation to the dou- Vbler 18. The signals from the doubler 18 also pass to phase shift networks 26 and 28 corresponding'in construction and operation to the networks and 22. The network 261may operate to shift the signals from the frequencyvdoubler 1S through an angle related Yto the frequency of the signals and to the time from the reception yof a retiected pulse to the formation of a particular clockV signal. The network 28 mayprovide a suitable phase shift such as approximately 45 degrees with respect to the phase shift provided by the vnetwork Y26.

Frequency doublers may be cascaded through'arny del sired number of stages in accordance Vwith the accuracy required in the measurements as to the time between the transmitted and received pulses. This is indicated by broken lines 30 in FIGURE l. In the final stages of the transmitting apparatus, the signals may be introduced to a frequency doubler 32 from the previous stage in the doubler 32 are in turn introduced to a frequency doubler 34 and to phase shift networks 36 and 38. The networks 36 and 38 may have the same phase relationship as the networks 14'and 16, the networks 20 and 22 and the networks 26 and 28.

The signals from the frequency -UREV 2).

input terminal of the delay line 58 and to a pulse i counter 60.

The frequency doubler 34, the phase shift networks 36,`

plication Serial Number 467,154 tiled November 5, 19,54,

by Leo P. Retzinger, Jr.'

The signals from the frequency doubler 34 are intro- -duced to the cathodes of diodes 70 and 72. The cathodesV `of the diodes 70 and 72 Vhave a common connection with one terminal of a resistance 73, the other terminal of vwhich is grounded. The diode 70 is includedin an and networkf73 with a diode 74,VV and the diode 72 is similarly included in an and.network 7S with a diodev s'76. The-'cathodes of thediodes 74 and 76'have a cornf-V mon connection through a line 77 with one of the!` output terminals inthe pulse counter 670 l(also shown in FIG- Y A resistance nected between the source 82 yand therplate of aidiode 83. The cathode of the diode 83has a common connection withan input terminal of an or network S4, otherin- Vput terminals of which are connected to and networks 86, S8, 91 and 93. The and network 86 has voltages applied to its input terminals through aline 87 from.k a second terminalV of the pulse counter 60 and directly fromY the phase Vshift network V36. Similarly, voltages are applied to input terminals' of the iand networkSS from the phase shift networkV 14 and through aline V89 The signals from the oscillatorrl) and the frequency doublers such as the doublers 12, V1S, 32 and 34 are introduced to a linear mixer 40 and the output from the mixer may be applied to amplifiers 42. References t0 suitable mixers of this type may be found, for example, in the Radiatron DesignersfHandbook, Langford Smith (Fourth Edition) 1952, pages'799-805, this handbook being reproduced and distributed bythe RCA Victor Division of the Radio Corporation ofV America, Harrison,

from a third terminal of .the counter 60. neryvoltages are applied to. the Vinput terminals of the and network 91 from the phase shift network 20 and from a-fourth output terminal ofthe pulse counter 60.

' Voltages are also applied V-torthe input terminal of the ,and7 network 93 from'the'phase shift network 26 and from a shift output terminal of the'counter60. "The -and networks 86 Vand 88 may be constructed'in a manner similar-to the and network formed by the Vdiodes 7o man.

The output'signals from the or network 84 pass to the platesV of Ydiodes 90Yand 92 and Vto one terminal of New Jersey. The signals from the amplifiers 42 pass in e turn to a diiferentiator 44 which may be constructed in a manner similar to the differentiators which are shown in FIGURE 3 and which will be describedV in detail subsequently. p

The diiferentiator 44 may be coupled to a magnetron indicated in block form 46. Although the magnetron 46 is shown in FIGURE 1, other apparatus such as Va klystron may also be used. By Vcoupling the differentiator 44 to the 'magnetron 46, the magnetron maybe triggered into oscillation upon the production of a particular i.

signal in the differentiator 44. The signals fromV the magnetron 46 are introduced to an antenna 48 for transmission by the antenna Von a wireless basis to a distant object.

The signals reflected from the distant object are received at the transmitting position by the antenna 49V of a receiver 50 shown in block form in FIGUREYZ.` The signals are introduced to a detector 52,which demodulates the signals and passes the signals to a diferentiatorVV 54. The differentiator 54v is coupled to an input terminal of an amplifier 56, another input terminal of which receives the output signals from a delay line S8. llfhe output Yterminal of the amplifier 56 is connected to the a resistance 94 having its other terminalV grounded. TheV Y j cathoderof the VdioderStl) receives the voltages on the left output terminal of a flip-flop 96 and the cathode of the diode 92 has signals applied to it from the amplifier 56 Valso showninFIGUREZ. f i

The flip-flop 96 may be constructed in a conventional manner such as is shown and described in co-pending application Serial Number 467,154, filed November 5, V1954,

by Leo P. VRetzinger,V Jr.'vr As such, the flip-nop 96 Vmay be provided with two output terminals shown'as left and right output'termin'als in FIGURE 3. TheV flip-flop 96 may also be provided with two input terminals shown as left andrright input terminals in FIGURE 3. The right input terminal of the-ilip-op 96 is shown in FIGURES as being connected Vto'the plate of a'diodeV 97. fThe cathode of the diode 97 is connected tothe Vctu'nrnonter- Vminal between a capacitance 98 and a resistance 99. The

capacitance 98 andthe Vresistance 99 are in series across the resistance 94.

A Just as the plates of the` diodes 70 and 74 have positive voltages Yapplied to them from the source 82 through ktherresistance '80, Vpositivenvoltages are appliedfthrough a resistancer'100'to the plates Vof, the diodes 72 and 76 and to the plate ofY a diode 10,2. VTheV cathode of the diode.102 is connected to an or network 104,-which also receives signals from and.networksl95,97, 106

and 108. Connections are made to input terminalsY of the and'network 166 from the phase shift network 38- and throughthe 1ine87 from the. second terminal 0f the The circuitry shown in FIGURE' Y In like maucounter 60. The and network 108 has input terminals connected to the phase shift network 16 and through the line 89 from the third terminal of the counter 60. The and network 95 has input terminals connected to the phase shift network 28 and to the fourth output terminal of the counter 60. The and network 97 has input terminals connected to the phase shift network 22 and to the first output terminal of the counter 60. The and networks 95, 97, 106 and 108 may be constructed in a manner similar to that formed by the diodes 72 and 76.

The Signals passing through the or network 104 are introduced to the cathode of a diode 110 associated with a diode 112. A positive voltage is applied from the source S2 to the plates of the diodes 110 and 112 through a suitable resistance 114. The cathode of the diode 112 is connected to the left output terminal of the flip-flop 96. The cathode of the diode 110 is connected to the plate of a diode 116 and to one terminal of a resistance 11S having its other terminal grounded.

The voltage across the resistance 11% is introduced to the grid of a tube 120. A positive voltage is applied from the source S2 to the plate of the tube and the ,cathode of the tube 120 is connected to one terminal of a resistance 122 having its other terminal grounded. A connection is also made from the cathode of the tube 120 to the cathode of a diode 124 having its plate connected to one terminal of a capacitance 126. The other terminal of the capacitance 126 has common connections with the cathode of the diode 116 and the output terminal of the amplifier S6.

A positive voltage is applied to the plate of the diode 124 through a resistance 130 from the voltage source 82. A resistance 132 and a diode 134 are in series across the resistance 130 such that the cathode of the diode 134 is connected to the resistance 130 and the plate of the diode is connected to the resistance 132. The plate of vthe diode 134 also has a common connection with the plate of a diode 136.

The cathode of the diode 136 is connected to the voltage source 82 to receive a positive voltage having a lower amplitude than the potential applied to such members as the resistances 130 and 132. A capacitance 138 and a resistance 140 are in series between the plate of the diode 134 and ground. The cathode of a diode 142 is connected to the common terminal between the capacitance 138 and the resistance 140. The voltage on the plate of 'the diode 142 is introduced to the left input terminal of the dip-flop 96.

The oscillator in FIGURE l is adapted to generate signals at a particular frequency such as approximately 150 cycles per second when an accuracy of one yard is desired in a range of approximately 200,000 yards between the antenna 4S and the distant object. The signals generated by the oscillator 10 and filtered and operated upon in other ways to have substantially a sinusoidal configuration. The signals from the oscillator 10 are introduced to the doubler 12 which acts upon the signals to produce signals having a frequency such as approximately 300 cycles per second. The doubler 18 in turn produces signals at approximately 600 cycles per second.

Each of the succeeding doublers such as the doublers 32 and 34 acts upon the signals introduced to it to produce signals having a frequency substantially twice as great as the frequency of the introduced signals. The signals produced by each of the doublers may have substantially sinusoidal wave shapes. When an accuracy of approximately one yard in a range of approximately 200,000 yards is desired, the doubler 34 may produce signals at a frequency such as 30 rnegacycles per second.

The signals from the oscillator 10 and each of the doublers such as the doublers 12, 18, 32 and 34 are introduced to the linear mixer 40. The mixer combines these signals without distortion and without the production of beat frequencies to produce signals indicated at 200 in FIGURE 4. Each of the signals 200 has a sharp leading edge 202 and a trailing edge 204 which is considerably more shallow in slope than the leading edge.

The signals 200 are amplified in the stages 42 and introduced to the differentiator 44. The stage 44 differentiates the signals 200 to produce signals having, at any instant, amplitudes dependent upon the rate of change of the signals 200 at that instant. Since the leading edges 202 of the signals 200 are quite sharp, the differentiator 44 acts to produce spiked signals 206 when the leading edges 202 of the signals 200 are introduced to the differentiator. The spiked signals 206 have amplitudes considerably greater than the amplitudes of signals 208 produced by the differentiator 44 when the trailing edges 204 of the signals 200 are introduced to the dilferentiator. This results from the relatively shallow slope which occurs in the trailing edges 204 of the signals 200.

The triggering signal produced by the differentiator 44 is introduced to the magnetron 46 to trigger the magnetron into a state of oscillation. The magnetron 46 produces oscillatory signals at a relatively high frequency for a relatively short period of time. This causes the oscillatory signals produced by the magnetron 46 to have an envelope in the shape of a pulse. These oscillatory signals are introduced to the antenna 48 for transmission by radiation therefrom. When the oscillatory signals strike an object removed from the antenna 48, the signals are reiiected by the object in a manner similar to that obtained in radar systems now in use.

The signals refiected from the distant object reach the receiver 50 in FIGURE 2. The signals reaching the receiver 50 are introduced to the detector 52 which acts upon these signals to remove the oscillatory signals produced by the magnetron 46. ln this Way, the signals passing through the detector 52 are in the form of a pulse representing the envelope of the signals transmitted by the antenna 48 and reaching the receiver 50. The leading edge of the pulse from the detector 52 is differentiated by the ditierentiator 54 to produce a sharply spiked signal having a positive amplitude.

The sharp signal of positive amplitude from the differentiator S4 is amplified by the stages 56 and introduced to the delay line 58. The line 58 delays the signal from the amplifier 56 by a particular period of time, which is preferably relatively short. For example, this period of time may be in the order of one microsecond. After being delayed, the signal from the delay line 5S is fed back to the amplifier 56 for passage through the amplifier and for subsequent introduction to the delay line. in this way, the amplifier 56 and the delay line 58 operate to produce signals periodically. These periodic signals may be considered as clock signals for purposes of the subsequent discussion.

The clock signals produced by the amplifier 56 and the delay line 58 are introduced to the counter 60 to trigger the counter. Since the counter 60 is constructed in a conventional manner from a plurality of flip-flops in a cascade arrangement, the counter operates to indicate in binary form the number of signals introduced to the counter from the amplifier 56. For each count, the counter 60 operates to produce a relatively high voltage on a different output terminal. For example, the counter 60 provides a relatively high voltage on the line 77 for an indication in binary form of the decimal value l and a relatively high voltage on the line 87 for an indication in binary form of the decimal value 2 and so on.

Upon the introduction of the first signal to the counter 60, an indication in binary form of the decimal value l is produced by the counter. This causes a relatively high voltage to be introduced through the line 77 to the cathodes of the diodes 74 and 76 in FIGURE 3. When a relatively high voltage is introduced to the cathode of the diode 74, the and network formed by the diodes 70 and 74 becomes prepared for operation. The and network fornied by the diodes 70 and 74 actually operates to produce a signal when a signal of positive polarityV is introduced to the cathode of the diode '70 from the frequency doubler 34 at the time that a high voltage is introduced to the cathode of the diode 74 from the pulse counter 60.

The and network formed by the diodes 70 and 74 operates upon the simultaneous introduction of high voltages to the cathodes of the diodes since these high voltages prevent current from flowing through a circuit in-V cluding the voltage source S2, the resistance 89 and the diodes. Since no current is flowing through therresistance 80, a voltage drop is not produced across the resistance. This causes the voltages'on the plates of the diodes 70 and 74 to approachrthe voltage from the source S2. v

Because Vof the relativelyhigh voltage on the plates of the diodes 70 and 74, current flows through a circuit including the diode 83, the or network 84 and the'resistance 94. The current flowing through the resistance 94 Vproduces a relatively high voltage across the resistance. Because of the relatively high voltage produced across the'resistance 94, relatively high voltages are introduced to the plates of the diodes 90 and 92.

In addition to the high voltages introduced to the plates of the diodes 90 and 92, voltages are also introduced to the cathodes of the diodes. For example, relatively high voltages may be simultaneously introduced to the cathodes of the diodes 92 and 99 from the ampliiier 56 and the left output terminal ofthe ilip-op 96. Because of the high voltages on the cathodes of the diodes 90 and 92, current cannot flow through the diodes even Lthough the voltage on the plates of the diodes maybe high. Since current cannot liow through the diodes 9i) and 92, the voltage on the plates of the diodes remains relatively high. Y Y

The high voltage introduced to the cathode of the diode' 92 occurs only on an instantaneous basis because it represents a yclockV signal correspondingto the received pulse. During the occurrence of this clocksignal, the positive voltage produced on the plates v.of Vthe diodes 90 and 92 causes current to ow through the resistance 94. This current produces a relatively high voltage across the resistance 94.

At the end of the signal from the amplifier 56, the voltage on the cathode of the diode 92 drops to a relatively low value. Since the voltage on the Vplate of the diode 92 would now be greater than the voltage'on theVV cathode ofY the diode, current ows through the diode. The ow of current through the diode 92 causes arelatively low impedance to be produced across the diode.V

voltage on the cathode of the diode.

The low voltage produced on the plate of the diode 92 Y causes the current flowing through the resistance 94 to become interrupted or at least limited such thatV a relatheip-Vflop 96 and on the basis of a positive signal from cuit including the source 82, the resistance 80, the diode Y.

'70 and the resistance 73.

The voltage drop produced across the resistance'SOr by the flow of current causes a relatively low voltage 'to be applied to the plate of the diode 83. This low voltage is in turn applied through the or network 84 to the plates of the diode 90 Vand 92. V,Since the voltage on the plates of the Vdiodes 90 and'i92 is relatively low, arrelatively low voltage is producedvacrossthe resistance V94. This preventsthepvoltage across the resistance 914 from decreasing at the end of the signal from the amplilier 56; Since a negative signalris not'produced across the'resistancec94 at the end ofthe signal of the amplifier 55, no triggering L signal can be Vproduced bythe action of the capacitance 93 and the resistance 99.k Thisrpreventsga triggering signal from passing through the diode 97 Vto trigger the ipi flop, 96 to its false, state. Y

A relatively low voltage Yon the left output terminal ofV the flip-flop 96 produces the same result as described in the preceding paragraph. This low voltage causes a low voltage to be introduced to the cathodeof the diode V90 and a low voltage'to be produced Von the plate ofithe diode because of theV ow of current through the diode. This lowvoltage limits any flow of current'rthrough the resistance'94 and prevents ahigh voltage from being produced across Vthe resistance. BecauseV of this, the voltage across the resistance 94 remains substantially constant at the end of the clockvsignal Vfrom the amplifier 56. Since a .constantV voltage is produced across the resistance 94, a negative triggering signal cannot beV producedby `the action-of Vthe capacitance 98 and the ,ref

tively low voltage isV produced across the resistance. Y

Since the voltage across the resistance 94 changes from a relatively high value to a relatively low value, a negative signal is produced on the plates of the diodes 90 and 92.V This negative signal is differentiated by the capacitance 98 and the resistance 99 to produce across the resistance 99 a relatively sharp triggering signal of nega-Y tive polarity. Y

The negative triggering signal produced Vacross the resistance 99 passes through the diode 97 because of the .particular manner in which the diode is connected in the sistance 99.` This prevents a signal from passing through the diode 97 to triggerrthe flip-flop 96 to its false state.

Y The cathodes of the diodes 72 and 76 receive the signalsV from the frequency doubler 34 and the'pulse counter'60f` in armannerrsimilar to theA diodes and 74. Because` of this, a relatively high voltage is produced on the plates Y on the plates of the diodes 72 and 76 at the same time that a relatively high voltage is produced on the plates f L ofthe diodes 70 and 74. This high voltage causes current 'Y c to ow through a circuit including the diode 102 the 0r network 104 and the Yresistance `118. VThe tlow ot` cur-` rent through the resistance 118 produces a relativelyV high voltage across a resistance for introductionto the 4gridY of the tube 120.

The high voltage'introduced to the grid of the tube 120 makes the tube conductive such that current ows through c a circuit including the voltage source 82, the tube and the resistance 122. This current produces a high voltage across the resistance 122 for introduction to the cathode of the diode 124. Since a high voltage is introduced'to the cathode of the diode 124, only a limited current can flow through a circuit including the voltage source`82, the resistance 130,V the diode and the resistance 122. Because of the limited flow of current through the resistance 130,`

a relatively low voltage drop is produced across the re- 'When a relatively high voltage is appliedtothe cathode of the vdiode 134, the. voltage on thecathode ofthe diode exceeds Vthe voltage on the plate. .TheV relativelyjlow voltage onV the plate of the diode 134 is producedbyra. iiow of'current through aV circuit which includes the voltf" Y age source, 82, the `resistance 132 and the diode 13@A f Since the voltage on the cathode Vfof the diodeVV 134 is greater than the voltage on'the. plate,'the Ycathode of the diode can receive a negative signal without having its potential drop below that of the plate.

A negative signal is produced at the end of they clock signal from the amplifier 56 and is introduced through the capacitance 126 to the cathode of the diode 134.

YSince the cathode of the diode 134 cannot swing negative with respect to the plate of the diode at the end of the clock signal from the amplier 56, a negative signal cannot be produced on the plate of the diode. This prevents a signal from passing through the capacitance 138 and the diode 142 to the left input terminal of the flip-flop 96. In this way, the ip-fiop 96 cannot be triggered to its true state upon the simultaneous introduction of relatively high voltages to the cathodes of the diodes 72 and 76.

It may sometimes happen that the cathode of the diode 72 may receive a negative signal from the frequency doubler 34 at the time that the cathode of the diode 76 has a relatively high voltage introduced to it from the counter 69. When this occurs, current flows through a circuit including the voltage source 82, the resistance 100, the diode '72 and the resistance 73. This current produces a voltage drop across the resistance 100 and causes a relatively low voltage to be produced on the 'plates of the diodes 72 and 76.

The low voltage on the plates of the diodes 72 and 76 in turn causes a relatively low voltage to be produced across the resistance 118. Because of the relatively low voltage across the resistance 118, the tube 120 remains cut oi and prevents current from owing through the resistance 122 to produce a positive voltage across the resistance. This low voltage is introduced to the cathode of the diode 124.

Upon the introduction of a low voltage to the cathode of the diode 124, a relatively large current is able to ow through a circuit including the voltage source S2, the resistance 130, the diode 124 and the resistance 122. This current produces a relatively large voltage drop across the resistance 130 such that a relatively low voltage is introduced to the cathode of the diode 134. As previously described, a relatively low voltage is also introduced to the plate of the diode 134 because of the ow of current through a circuit including the voltage source 82, the resistance 132 and the diode 136.

Since the voltages on the cathode and plate of the diode 134 are both relatively low, the voltage on the cathode of the diode is able to fall below the voltage on the diode plate at the end of the clock signal from the amplifier 56. -The voltage on the plate of the diode 134 follows the decrease in the voltage on the cathode to produce a negative signal. This signal is differentiated by the action of the capacitance 138 and the resistance 140 to produce a negative triggering signal. The negative triggering signal passes through the diode 142 to the left input terminal of the Hip-flop 96. The signal triggers the flip-flop 96 to its true state to produce a relatively high voltage on the left output terminal of the ilip-op and a relatively low voltage on the right output terminal of the ipflop.

The above discussion relating to the introduction of a triggering signal to the left input terminal of the flipop 96 has proceeded on the basis of the existence of `a relatively low voltage on the left output terminal of the ilip-tlop. When a relatively high voltage is introduced to the cathode of the diode 112 from the left output terminal of the ilip-op 96, this voltage controls the output of the network formed by the diodes 110 and 112. This high voltage produces a ow of current through the resistance 118 and a resistant ow of current through the tube 126 and the resistance 122 in a manner similar to that described above.

The flow of current through the resistance 122 causes a relatively high voltage to be produced across the resistance and on the cathode of the diode 124. This high voltage is transferred to the cathode of the diode 134 in a manner similar to that described above. The high voltage on the cathode of the diode 134 prevents a signal from passing through the diode at the end of the l@ clock signal from the ampliiier 56. A signal cannot pass to the flip-op 96 regardless of the operation of any of the logical networks shown at the bottom of FIGURE 3. These networks include the and network formed by the diodes 72 and 76 and the and networks 106 and 108. It will be seen from the above discussion that a triggering signal can pass to the right input terminal of the llipflop 96 only when a relatively high voltage is produced on 'the left output terminal of the flip-flop. Furthermore, a

triggering signal can pass to the left input terminal of the flip-flop 96 only upon the prior production of a relatively low voltage on the left output terminal of the ilip-op. For this reason the ip-flop 96 determines whether the and networks in the upper portion of FIGURE 3 or the and networks in the lower portion of FIGURE 3 are to control the introduction of input signals to the flip-dop.

lust as the ip-flop 96 controls whether the and networks in the lower or upper portion of FIGURE 3 are to pass triggering signals, the pulse counter 60 controls the particular and network which is activated. For example, the iiip-flop 96 may provide by its operation for the passage of a triggering signal from any one of the and networks S6, 88 or 91 or the network formed by the diodes 70 and 74. However, the pulse counter 60 operates to activate only the and network 86 upon an indication in binary form of the decimal value 2. In this way, the counter 60 operates to obtain an activation of the different and networks on a sequential basis in accordance with the advance of the count in the counter.

It may be seen from the above discussion that triggering signals are introduced to the right input terminal of the ilip-op 96 in accordance with the following logical equation:

where El: a triggering signal introduced to the right input terminal of the flip-flop 96;

P1=a relatively high voltage on the line 77 to indicate a count of l in the counter 66;

S1*=a signal of positive polarity from the frequency doubler 34;

P2=a relatively high voltage on the line 87 to indicate a count of 2" in the counter 6);

S2i =a signal of positive polarity from the plate shift network 36;

Pn=a relatively high voltage on the line 89 to indicate a count of "11 in the counter 60;

Sni-=a signal of positive polarity from the phase shift network 14;

M=a relatively high voltage on the left output terminal of the llip-llop 16; and

C=a clock signal from the ampliiier 56.

As is well known in computer terminology, the sign indicates an or relationship which would cause an El triggering signal to be produced when any of .the terms such as PlSli, P2S2*, etc. become true.

A logical equation can also be developed from the above discussion to indicate the introduction of triggering signals to the left input terminal of the flip-op 96. This logical equation is as follows:

clock signal 228.

megeve ll Y It should Ybe appreciated that the flip-flop 96 notonly controls the selection ofthe particular phase shift network in the successive pair of networks butalso provides signals representing the output from the networks. These indications are represented by the pattern of high Yaridrlow voltages on the right output terminal of the flip-flop 96. A low voltage on the right' output terminal of the ilip-flop 96 represents a value of "0 for a particular binary digit and a high voltage on the right output terminal of the flipilop represents a value of l for the binary digit.

The operation of the apparatus will now be explained with reference to a particular example such as that shown in FIGURE 5. In this example, the signals produced by the oscillator and the frequency doublers such as the stages 12, 18,327and 34 in FIGURE 1 have a particular `phase relationship at the time Ythat the reflected pulse reaches the receiver 59. As maybeV seen kin FIGURE 5, a relatively highV voltage indicated at V220 may exist on the left output terminal of the flip-flop 96 before the reception of the reflected pulse.l This causesV diodes 74 and 76. Since a relatively high voltage existsV on the left output terminal ofthe flip-flop 96, only the and network formed by the diodes 7G and 74 can f produce a triggering signal. Y

In the example set forth in FIGURE 5, the signal from the frequency doubler 34 has a negative polarity at the time that a high voltage is produced on the line 77`. This prevents a signalfrom passing to the right input terminal of the flip-flop 96 as described fully above.l Because of this, a relatively high voltage continues to exist on the left'output terminal of the flip-flop 96 as illustrated at 224 in FIGURE 5. Since a relatively high voltage is produced on the left output terminal of the flip-flop 96, arelatively low voltage is produced on the right output terminal of the flip-flop, as indicated at 226 in FIGURE 5. Y

After a particular time, the clock signal 222 produced by the amplifiers 56 circulates through the delay line 58 for introduction to the input terminal yof the amplifier. This causes a second clock signal to be produced by the amplifier, as indicated at 228 in FIGURE 5. Upon the production of the clock signal 228, a relatively high voltrage is produced by the counter 60 on the line 87. This voltage is introduced to the and networks 86 10610V prepare the and networks for activation. Y

Y Because of the relatively high voltage on the left output Vterminal of the flip-flop 96, only the and network 86 can be effective in obtaining the` passage of a triggering signal to the flip-dop. At Vthe time that a relatively high voltage is produced on the line 87, the signal frornthe phase shift network 36 may have a positive polarity.V The shift in phase provided by the network 36 may be related to the frequency of the signals introduced to the network Yand to the time between the signals 222 and V228. In this way, the network 36 operates to compensate for any errors which mightresultV from the time interval between the received pulse and the production .of Ythe second l2 false state of operation'of the flip-flop 96,-a relatively ,high voltage is produced on the right output terminal of the flip-flop, as indicated at 230 in FIGURE 5, and a relatively low voltage is produced on the left output terminal of the flip-flop, as indicated at 232 in FIGURE 5.

After a'particular period of time,the ampliier'56 and the delay line` 58 operate to produce a third clock signal 234. When the clock signal 234 is produced,4 it causes the Y andfnetwork 95 to become prepared for activation. TheV the associated phase shift network 28. As described above,

the occurrence of a signalof positive polarity Zfrom the associated phase shift network prevents'A a triggering signal from passing to the left input terminal of the flip-flop 96. Y

This Vcauses the relatively high voltageto be' maintained on the right output terminal of the flip-flop 96,V as indicatedV at 236 in FIGURE 5. Because of the'relatively high volt? Vage on the right output terminal of the flip-flop 96, a relatively low voltage is maintained onthe left output terminal of the flip-flop 96, as indicated at 238 in FIGURES; y

In like manner, signals are produced on the rightV output terminal of the flip-flop 96 upon the production of suc-V cessive clock signals to'indicate in digital form the time i between the transmission of a Vpulse and the reception offV As shown inf FIGURE 5, aY relatively Vlow voltage may be produced onV the left output terminal of the flip-flop 96 whenthe signals the pulse reflected from a distant object;

in the phase shift networks 20 and 22 are tested'for their polarity. Y The low voltageon the left Voutput'terminal of f the flip-flop 96 may be indicated at 240. Since a relatively low voltage'is produced on the'left output terminal of the flip-flop 96, a relatively high voltage indicated Vat 77242 is simultaneously^ produced on the right ,output terminal of the flipflop. Y Y

A clock signal 244 may be produced by the operation y of theamplifler 56 and the delayline58 after. the low voltage 240 has been obtained on therleft output terminal of the flip-flop 96. Y When theclock ksignal 244 is produced, Va high voltage is introduced from theY pulse counterY Y Y `60 through the line S9 to the and networks 88 and 108.

,Since a relatively low voltage is produced on theV left output terminal ofthe flip-flop 96, onlyv the andfnetwork 108 can'become activated. i Y 1 In theV exampleV shown in FIGURE 5, a signal of nega.-

Y tive polarity is introduced to the and network 108 from is produced on the line 89. The network 16 operates on the phaseshift network 16 at theV time Vthat a high voltage the signals from the oscillatorlt) to shiftthe phase of the .signals through an angle dependent uponthe frequency of tive polarity fronrthe network 16 at the time that itibe-V similar to that described above ,'This signal triggersthe flip-'flop 96 Yto its true state as represented Yby arelatively the signals and upon the total delay between therreception i of the reflected pulse and the production of theclockVY signal244. Y Y v K Since the andV network'108rreceives a signal of nega-V comes Vprepared for activation, a triggering signal passes toV theleft input jterminal ofY the flip-flop 96 in VaV manner Y high voltage on; the left Voutput Vterminal of the flip-flop Because of the simultaneous introducuon of relatively y 96. VThis voltage .is indicated atj248-in FIGURE 5. Be-

cau'seof theproduction of a relatively high voltage on the I vleft output terminal ofthe flip-flop 92, arelatively low voltage is produced on the right outputterminal of -the ip-op,as indicated at V250 .inV FIGURE 5.

The signalsVY produced on theright output terminal'rofV the ilip-flop'96' represent in digital form'the time; between the transmission of a pulse'towardthe distant object and the receptionfof the pulse reflected from the `.distant ob-V FIGURE 5,'V asignarrposi-V nal of the flip-flop 96 are indicated at 226, 230 and 236 in FIGURE and are intended to represent digital indications of Oll, where the least significant digit is at the left. This is equivalent to (2) (0H-(21) (1)-1-(22) (l)=6. By determining the time between the transmitted and reflected pulses, the distance between the antenna 4S in FIG- URE l and the distant object can be determined by a simple conversion factor. A digital display unit 252 is coupled to the right output terminal of the flip-flop 96. This unit, for example, may be constructed in well known manner to include a plurality of flip-flops. These flip-flops may all be initially set to their false state. Then, under the control of the pulse counter 60, a logic path is prepared to successive ones of the flip-flops. Wheneverthe flipop 96 is set true during the particular successive intervals, the corresponding flip-flops in the unit 252 are respectively set true. Appropriate indicating means may be coupled to the flip-ops in the display unit 252 so that the states of the flip-flops at the termination of the measuring interval may be indicated. These states, of course, will correspond to the successive states of the flip-flop 96 during the measuring interval.

The apparatus described above has severalimportant advantages. The apparatus produces a timing signal at an optimum instant in accordance with a particular phase relationship between a signal at a fundamental and a plurality of harmonic frequencies. It then uses this timing signal to produce a pulse for transmission toward a distant object and for reflection from the object. In this way, the time from the transmission of the pulse can be accurately measured. t v The apparatus is also advantageous in that it requires a minimum number of stages with Wide band characteristics. Because of this, power amplification can be obtained without any need for a large number of intermediate1 stages. This causes savings to be obtained in space, weignt, cost and power consumption. It also permits the use of transistors since transistors at present do not have wide band characteristics. By using transistors, furthensavings in cost, weight, complexity and power consumption can be obtained.

A further advantage is obtained by producing output signals on a digital basis. As is well known, digital representations provide more accuracy than analog representations such as single voltages. The digital representations are obtained without any possibilities of ambiguity resulting from occurrences of signals from the oscillator and the frequency doublers such as the stages 12, 18,52 and 34 at the time that the signals are changing in polarity. This results from the use of the particular type of converter shown in FIGURE 3 and described fully above.

l. In combination: generating means for providing signals at a fundamental frequency and particular harmonic frequencies, means coupled to the generating means and responsive to the signals at the fundamental frequency and at the particular harmonic frequencies for combining these signals to produce a timing signal, means coupled to the combining means and responsive to said timing signal for producing a pulse for transmission to a distant object, means for receiving a reflected pulse from the distant object produced by reflection of the transmitted pulse thereby, and means responsive to the reflected pulse and to the phases of the signals at the fundamental and harmonic frequencies at the time of the reception of the reflected pulse to provide digital indications as to the time between the production of the timing signal and the reception of the reflected pulse.

2. In combination: generating means for providing a fundamental signal at a fundamental frequency and for providing particular harmonic signals having frequencies at respective harmonics of the fundamental frequency, means coupled to the generating means for combining the signals to produce a resultant timing signal, means coupled to the combination means for differentiating the resultant signal to produce a relatively sharp triggering signal, means coupled to the differential means and responsive to the triggering signal for producing a pulse for transmission to a distant object, means for receiving a reflected pulse from the object produced by reflection of the transmitted pulse thereby, means coupled to the receiving means and responsive to the reflected pulse for producing a circulation of the reflected pulse at spaced intervals of time to provide a series of clock pulses, and means responsive to the clock pulses to test the phase of the harmonic and fundamental signals in order of their decreasing frequency.

3. In combination: generating means for providing signals at a fundamental frequency and at particular harmonic frequencies, means coupled to the generating means for combining the signals at the fundamental frequency and at the particular harmonic frequencies to produce a timing signal, means coupled to the combining means and triggered by the timing signal for producing a pulse for transmission to a distant object, means for receiving a reflected pulse from the object produced by reflection of the transmitted pulse thereby, means coupled to the receiving means and responsive to the reflected pulse for producing clock signals at periodic intervals after the reception of the reflected pulse, and means responsive t0 the clock signals and to the signals at the fundamental frequency and at the particular harmonic frequencies for determining the phase of the signals at the fundamental and harmonic frequencies upon the occurrence of the successive clock signals to provide a plurality of signals digitally representing the time between the production of the timing signal and the reception of the reflected pulse.

4. In combination: generating means for providing a plurality of oscillatory signals having frequencies Whose values are geometiiically related to one another, combining means coupled to the generating means and responsive to the plurality of oscillatory signals for producing a triggering signal, means coupled to the combining means and responsive to the triggering signal for producing a pulse for transmission to a distant object; means for receiving a reflected pulse from the distant object produced by reflection of the transmitted pulse thereby, means coupled to the receiving means and responsive to the reflected pulse for producing clock signals periodically after such reception, and means coupled to said generating means and to said last-mentioned producing means and responsive to the phase of successive oscillatory signals in the plurality during successive occurrences of the clock signals to provide a plurality of ouptut signals digitally representing the time between the occurrence of the triggering signal and the reception of the pulse from the distant object. 5. In combination: generating means for providing a first plurality of signals having frequencies whose values are geometrically related to one another, combining means coupled to the generating means for combining the signals of said plurality upon the occurrence of a particular phase relationship of such signals to produce a pulse for transmission toward a distant object, means for receiving a reflected pulse from the removed object to the transmitted pulse means for receiving the pulse from the distant object produced by reflection of the transmitted pulse thereby, means coupled to the receiving means for producing a series of regularly timed clock pulses in response to said reflected pulse, and means coupled to said generating means and to said last-mentioned producing means and responsive to said clock pulses and to phases of said signals of said first plurality to produce a series of signals digitally representing the phase of the signals in the first plurality at the time of reception of the pulse from the removed object.

6. In combination: generating means for providing a first plurality of signals having frequencies whose values are geometrically related to one another, means coupled to said generating means responsive to the signals ofthe first plurality for producing a relatively sharp triggering signal, means coupled to said producing means and responsive to the triggering signal to produce a pulse for transmission toward a distant object, receiving means for receiving a reflected pulse from the object produced by the reflection thereby of the transmitted pulse, means coupled to the receiving means Vresponsive to the reflected pulse received by the receiving means for producing regularly recurring timing signals, a bistable member, and means coupled-to said generating means and to the timing signal-producing means for sequentially activating the bistable member upon the production of the timing signals and inaccordance with the phases of the signals in the first Y plurality to provideV a plurality of output signals representing in digital form the time between the production of the triggering, signal and the reception of the reilected pulse. t Y

V7. In combination: generating means including a series of networks for respectively producing-signals having frequencies whose values are geometrically related to one another, means coupled to said generating means for producing a trigger signal, means coupled totsaid trigger sigsaid receiving means and responsive to the'relected pulse for producing regularly recurring timing signals, means including a plurality of and networks respectively coupled to said pairs of phase-shift networks, means coupled to saidrtiming signal-producing means forV sequentially preparing said pairs of and networks for activation, a bistable network, and circuit means coupled to said and networks for triggernig said bistable network between two stable states in response to signals derived from said and networks. Y 1

l0. In combination: generating means for providing signals at a fundamental frequency and at a plurality of harmonic frequencies whose values are Vgeon'letrically related to the fundamental frequency and Vto one another,

means coupled to said generating means andresponsive to the signalsv at the fundamental frequency and at the harmonic-frequencies for shifting the phase'ofV each of such signals to provide at each frequency a pair of signals ',having a particular phase relationship to each other, means-` vcoupled to said generating means and responsive to the Y signals at the fundamental and harmonic frequencies forY nal producing means and responsive to said trigger signal Y for producing a pulse for transmission toward a distant object, means for receiving a reilected pulse from the distant object produced by the transmitted pulse, means coupled to said receiving means and responsive to said reflected pulse for producing periodic timing signals, means including a plurality of pairs of and network means respectively coupled to said series of networks, means coupled to said timing signal-producing meansfor sequentially preparing said pair of and network means for activation, a bistable network, and means coupled to said and network means for triggering said bistable network be tween two stable states in response to signals derived from said and network means.

' 8. In combination: generating means including a plurality of frequency doubler networks for respectively producing signals at a fundamental frequencyand at a plurality of harmonic frequencies, means coupled to said generating means and responsive Vtothesignals produced said trigger signal-producing means and responsive to said triggersignal for producing a pulse for transmission toward a distant object, means for receiving a reflectedV pulse from the distant object produced'by the transmitted pulse, means coupled to said receiving means and responsive tosaid reflected pulse Vfor-producing a series of regularly recurringclock pulses, means including a plurality of pairs of and networks respectively coupled to said frequency doubler networks, means including a counter network coupled to said timing signal-producing means-for sequentially preparing said pairs of and net-'- another, means coupled to said generating meansrand responsive to the signals having the fundamental frequency and the harmonic frequencies for combining these signals Vto produce a trigger signal upon the occurrence of a particular phase relationship in the fundamental and har- Vmonic frequencies, means coupled Vto said combining,

' thereby for producing a trigger signal, means coupled to Y combining such signals to produce a trigger signal, means coupled toV said combining means and responsive to/said trigger signal for producing a pulse for transmission towards a distant object, means for receiving fromV thedistant objectrof a reflected pulse produced by the ,trans-V mitted pulse, a bistable member havingrst and second states of operation, a plurality of Vand networks respectively coupled to said phaseshifting means to receive respective'ones of the pairs of signals at the fundamental and at the harmonic frequencies and each paired with the and network receiving the other signal at the same V* frequency, means coupled to'said receiving means andrto the and networks in the plurality for sequentially select-Vi Ying successive pairs of such and networks, and means coupled to said and. networks in the plurality and to said bistable member for'triggering said bistable member in accordance with the phase of the signal introduced to the sequentially selected pairsy of tandf.ne'tworks inthe i plurality. L f Y t i t 11. In combination: generating means for producing signals at a fundamental frequencyand at a plurality of'Y Y harmonic frequencies whose values arege'ornetrically re- 1 lated to therfundamental frequency andk to oneanother,

`meanscoupled to said generating means and Yresponsive tothe signals at the fundamental frequency-and 'at' the lharmonic frequencies for shifting the phasetof each ofY Ysuch signals to provide atteach frequency a pair of sigt nals having a Vparticular phase relationship to each other, 1 means coupled to said Vgenerating means and responsive l to the *signals at the fundamental and harmonicrfrequen- Y cies for combiningsuch signals to produce a trigger sig?V means and responsiverto the trigger signal Vto produceanlV energy pulse for transmission toward aV distant'object,

means for receiving from the object a reflected pulse 4producedby the transmitted pulse, a plurality of pairs of phase shifting networks coupled to said generating t nal, means coupled Vto said `combining means and responf Y sive to said triggersignal for producing a pulse for transmission toward a distant object, means for receiving from the Vdistant object a reflected pulse produced Vby the transmitted pulse, means coupled to said receiving means and responsive to the received pulse for producing periodic timing signals, counter-means coupled to saidlast named t means. andresponsive-to thel periodic timing signals for producing-successive selecting signals, a bistable memberj having first-,and second states of'operation, a pluralityV of ,and networks respectivelyV coupled tofsaid Vphase,Y

shifting means to receive respective ones ofthe-pairs'of means, each of the tandfnetworks'in,the ,pluralityY being paired'rwith the Vand` network in the plurality receiving the Y*other-signal at the same frequency and thepairs of and'networks being successively selected by said select- ,t t ing signals, and means coupled to the and networks in Vthe plurality for triggering-the bistable member in accordance with the phase of the respective signals from saidV 'i7 phase shifting means to the and networks of the successively selected pairs of and networks in the plurality.

12. In combination: generating means for providing signals at a fundamental frequency and particular harmonic frequencies, means coupled to the generating means and responsive to the signals at the fundamental frequency and the harmonic frequencies for combining these signals to produce a trigger signal, means coupled to the combining means and responsive to said trigger signal for producing a pulse for transmission to a distant object, means for receiving from the object a reflected pulse produced by the transmitted pulse, means coupled to the generating means and operative upon the signals at the fundamental and particular harmonic frequencies for providing at these frequencies pairs of signals in which the signals in each pair have a particular phase relationship to each other, means coupled to said last-named means and to said receiving means and successively operative upon the pair of signals at each frequency and responsive to the received pulse for successively selecting particular ones of said pairs of signals, and means coupled to said lastnamed means and responsive to successively selected signals therefrom for providing an output indication in accordance with the phase relationship of said signals at the fundamental and harmonic frequencies at the time of the reception of the reiiected pulse from the distant object.

13. In combination: generating means for providing oscillatory signals at a fundamental frequency and at particular harmonics of the fundamental frequency, means coupled to the generating means and responsive to the oscillatory signals for transmitting a pulse to a distant object, means for receiving a reected pulse from the distant object produced by the transmitted pulse, phase-shifting means coupled to said generating means for imparting phase-shifts to the oscillatory signals, means coupled to said receiving means and responsive to said reflected pulse for producing a series of timing signals related to the relative timing of the phase-shifted oscillatory signals, and network means coupled to said phase-shifting means and to said timing signal-producing means for producing output signals representative of the phase relationship of said fundamental and harmonic oscillatory signals at the time of reception of said reflected pulse by said receiving means.

14. A system for determining the time interval between a first pulse and a second pulse time-spaced from the first pulse, the system including: first means for producing oscillatory signals at a fundamental frequency and at particular harmonic frequencies of the fundamental frequency, circuit means coupled to said first producing means for developing said first pulse when said oscillatory signals at said fundamental and harmonic frequencies have a particular reference phase relationship, phaseshifting means coupled to said first producing means for imparting predetermined phase shifts to said oscillatory signals at said harmonic frequencies, second means for producing said second pulse, generating means coupled to said second producing means for producing a series of timing pulses in response to said second pulse, and further circuit means coupled to said phase-shifting means and to said timing pulse generating means for producing an output signal digitally indicating the relative phases of the oscillatory signals at the time of production of said second pulse.

15. A system for determining the time interval between a first pulse and a second pulse time-spaced from the first pulse, the system including: first means for producing oscillatory signals at a fundamental frequency and at particular harmonic frequencies of the fundamental frequency, circuit means coupled to said first producing means for developing said first pulse when said oscillatory signals at said fundamental and harmonic frequencies have a particular reference phase relationship, a plurality of phase-shifting networks coupled to said first producing means for imparting predetermined phase shifts to said oscillatory signals at said fundamental frequency and at successive ones of said harmonic frequencies, second means for producing said second pulse, generating means coupled to said second producing means for developing a series of timing pulses in response to said second pulse and having a timing related to the phase shifted oscillatory signals at said fundamental frequency and at said successive ones of said harmonic frequencies, and further circuit means coupled to said phase-shifting networks and to said timing pulse generating means for producing an output signal digitally representing the relative phases at the time of production of the second pulse of the oscillatory signals at said fundamental and harmonic frequencies.

16. A system for determining the time interval between a first pulse and a second pulse time-spaced from the rst pulse, the system including: first means for producing oscillatory signals at a fundamental frequency and at particular harmonic frequencies of the fundamental frequency, circuit means coupledlto said lirst producing means for developing said first pulse when said oscillatory signals at said fundamental and hamonic frequencies have a particular reference phase relationship, a plurality of pairs of phase-shifting networks coupled to said first producing means for imparting predetermined respective first and second phase shifts to said oscillatory signals at said fundamental frequency and at successive ones of said harmonic frequencies excepting the highest one of said harmonic frequencies, second means for producing said second pulse, generating means coupled to said second producing means for developing a series of timing pulses in response to said second pulse and having a timing related to the phase shifted oscillatory signals at said fundamental frequency and at said successive ones of said harmonic frequencies, and further circuit means including a bistable network coupled to said phaseshifting networks and to said first producing means and to said timing pulse generating means for producing an output signal digitally representing the relative phases at the time of production of the second pulse of the oscillatory signals at said fundamental and harmonic frequencies.

17. A system for determining the time interval between a first pulse and a second pulse time-spaced from the first pulse, the system including: first means for producing oscillatory signals at a fundamental frequency and at particular harmonic frequencies of the fundamental frequency, circuit means coupled to said first producing means for developing said rst pulse when said oscillatory signals at said fundamental and harmonic frequencies have a particular reference phase relationship, a plurality of pairs of phase-shifting networks coupled to said first producing means for imparting predetermined respective first and second phase shifts to said oscillatory signals at said fundamental frequency and at successive ones of said harmonic frequencies, second means for producing said second pulse, generating means coupled to said second producing means for developing a series of timing pulses in response to said second pulse and having a timing related to the phase shifted oscillatory signals at said fundamental frequency and at successive ones of said harmonic frequencies, a first plurality of and networks respectively coupled to a first of the phase-shifting networks of respective ones of said pairs, a second plurality of and networks respectively coupled to a second of the phase-shifting networks of respective ones of said pairs, and circuit means including a bistable network coupled to said first and second plurality of and networks and to said timing pulse generating means for producing an output signal digitally representing the relative phases at the time of production of the second pulse of the oscillatory signals at said fundamental and harmonic frequencies.

18. A system for determining the difference in time between first and second pulses and for producing a plul@ rality of output signals digitally representing such differences, means for developing an oscillatory signal having a fundamental frequency and particular harmonics of the fundamental `frequency, first means coupledto the signal developing means for producing a said iirst pulse at a time corresponding to a particular phase relationship of said fundamental and harmonics, second means for producing said second pulse, means coupled to said second producing means for generating a plurality of timing pulses at spaced intervals of time after the production of the second pulse, and means coupled to said second producing means and to said timing pulse generating means and responsive to the second pulse and to successive ones of said timing pulses for determining the relative phases of the harmonics and the fundamental in the oscillatory signal and for providing such a determination in the order of decreasing frequency of the particular harmonicsV and the fundamental frequency to produce a plurality of output signals digitally representing the separation in time between the first and second pulses.

19. A system for determining the difference in time between first and second pulses and for producing a plurality of output signals representing such differences, means for developing signals at a fundamental frequency and at particular harmonic frequencies, means coupied to said developing means and responsive to the signals at the fundamental frequency and at the harmonic fre quencies for combining these signals to produce the first pulse, a plurality of paired phase-shifting means coupled to said developing means and responsive to the signals at` said fundamental frequency and at said harmonic frequencies for producing at each of the fundamental and 2@ harmonic frequencies a pair of phase-shifted signals, means for producing said second pulse, means coupled to said last named producing means and responsive to the second pulse for periodically generating a series o f timing pulses, first circuit means coupled to said last named producing means and to said timing pulse Vgenerating means and responsive to the pairs of phase-shifted signals and to the timing pulses for producing control signals indicative of the relative phases of the fundamental and harmonics of the oscillatory signal, and second circuit means including a bistable network coupled to said iirst -circuit means for producing an output signal digitally representing the separation in timeV between the first pulse and the second pulse.

20. In combination as set forth in claim 14, including electrical circuitry responsive to the first pulse for trans` mitting a pulse toward a distant object for reliection from the distant object of a pulse produced by the transmitted pulse, and in which said second producing means is responsive to the pulse from the distant object to produce the second pulse.

References Cited in the file ofthis patent UNITED STATES PATENTS Australia May 26, 1949 

1. IN COMBINATION: GENERATING MEANS FOR PROVIDING SIGNALS AT A FUNDAMENTAL FREQUENCY AND PARTICULAR HARMONIC FREQUENCIES, MEANS COUPLED TO THE GENERATING MEANS AND RESPONSIVE TO THE SIGNALS AT THE FUNDAMENTAL FREQUENCY AND AT THE PARTICULAR HARMONIC FREQUENCIES FOR COMBINING THESE SIGNALS TO PRODUCE A TIMING SIGNAL, MEANS COUPLED TO THE COMBINING MEANS AND RESPONSIVE TO SAID TIMING SIGNAL FOR PRODUCING A PULSE FOR TRANSMISSION TO A DISTANT OBJECT, MEANS FOR RECEIVING A REFLECTED PULSE FROM THE DISTANT OBJECT PRODUCED BY REFLECTION OF THE TRANMITTED PULSE THEREBY, AND MEANS RESPONSIVE TO THE REFLECTED PULSE AND TO THE PHASES OF THE SIGNALS AT THE FUNDAMENTAL AND HARMONIC FREQUENCIES AT THE TIME OF THE RECEPTION OF THE REFLECTED PULSE TO PROVIDE DIGITAL INDICATIONS AS TO THE TIME BETWEEN THE PRODUCTION OF THE TIMING SIGNAL AND THE RECEPTION OF THE REFLECTED PULSE. 